1. Field of the Invention
The present invention relates generally to tape cassettes and, more particularly, is directed to a tape cassette suitable as a so-called color tape cassette of a video tape recorder (VTR).
2. Description of the Prior Art
In order to simplify the loading or unloading of a recording and reproducing magnetic tape in a video tape recorder, a tape cassette having a magnetic tape wound therein is useful. It is convenient for a user, when this tape cassette is loaded into the video tape recorder, if the video tape recorder/player can determine whether the magnetic tape within the tape cassette is in the rewound state (start mode) or whether the magnetic tape is in the wound state (end mode). For this reason, the tape cassette is generally provided with a mechanism, by which the start mode or the end mode of the magnetic tape can be detected from the outside of the cassette.
FIG. 1 shows such a prior-art tape cassette which is generally designated by reference number 1. In FIG. 1, reference numeral 2 denotes an upper cassette half, 3 a lower cassette half and a 4 magnetic tape. A transparent leader/trailer tape 4a is connected to the respective ends of the magnetic tape 4. A guard panel 5 protects the magnetic tape 4 from smudges, finger marks and so on. Transparent windows 6A, 6B are formed on the upper cassette half 2 so that the inside of the tape cassette can be visually confirmed.
FIG. 2 shows the side of the lower cassette half 3 of the prior-art tape cassette of the example shown in FIG. 1.
Referring to FIG. 2, it will be seen that the magnetic tape 4 is supplied from a supply reel 7A and is taken up by a take-up reel 7B through a guide pole 11, a tape guide 12, a front panel 3b of the lower cassette half 3, a tape guide 13 and a guide roller 14. The supply reel 7A is held between a reel flange 8A and a lower reel flange (not shown), and the take-up reel 7B is held between a reel flange 8B and a lower reel flange (not shown). Brake levers 9A and 9B are respectively engaged with lower reel flanges (not shown), and these brake levers 9A and 9B are operated by a release 10 from the outside.
Along the front panel 3b, arcuate front ribs 15 and 16 are formed to be substantially coaxial with the supply reel 7A and the take-up reel 7B, whereby a space 17 is formed between the magnetic tape 4 and the front rib 15. Also, a space 18 is formed on the front panel 3b. Loading posts (not shown) of a video tape recorder are inserted into these spaces 17 and 18 when the tape cassette is loaded into the video tape recorder. Through the cylindrical wall 19, there are provided lighting windows 19a and 19b in an opposing relation with an angular extent of substantially 180 degrees.
One end of a side wall 3a of the lower cassette half 3 near the side of the take-up reel 7B is recessed to form a partition 20 as shown in FIG. 3. The partition 20 is covered with the guard panel 5. As shown in FIG. 3, apertures 20a, 20b and a light receiving window 21 are formed through the partition 20. Two partitions 22, 23 extend from the lower cassette half 3 perpendicular to the partition 20 and aligned slits 22a, 23a are respectively formed on the partitions 22, 23. Rotating shafts 24c and 24d of a lid locking member 24 are engaged with the above-mentioned slits 22a and 23a, and the lid locking member 24 is generally spring-biased by a spring (not shown) in the direction shown by .theta. in FIG. 3. Accordingly, as, for example, shown in FIG. 1, a lock-releasing pin 24a and a lock lever 24b of the lid locking member 24 project to the outside through the apertures 20a and 20b of the partition 20, and the lock lever 24b is engaged with a lock slit 5a of the guard panel 5 (when the guard panel 5 is in its normally closed position). When the guard panel 5 is opened, as shown in FIG. 1, the engagement between the lock lever 24 and the lock slit 5a has to be released by inwardly pushing the lock releasing pin 24a.
A side wall 3c of the lower cassette half is parallel to the side wall 3a. Further, one end of the side wall 3c at its position near the side of the supply reel 7A is concave to provide a partition 25 covered with the guard panel 5 as shown in FIG. 4. As shown in FIG. 4, a light receiving window 26 of a slit configuration is formed in the partition 25.
In order for the video tape recorder to determine whether the magnetic tape 4 is in the start mode or in the end mode after the tape cassette 1 shown in the example of FIG. 1 is loaded into the video tape recorder, as shown in FIGS. 1 to 3, a light emitting element 27 is inserted into the cylindrical wall 19 of the lower cassette half 3 and a start sensor 28 and an end sensor 29, each formed of a light receiving element, are positioned outside the light receiving windows 21 and 26, respectively. When the transparent leader tape 4a intersects an optical axis L.sub.1 connecting the lighting window 19a and the light receiving window 21, the start sensor 28 generates a signal, while when the transparent trailer tape 4a intersects an optical axis L.sub.2 connecting the lighting window 19b and the light receiving window 26, the end sensor 29 generates a signal. Thus, the video tape recorder can determine whether the magnetic tape 4 is in the start mode or in the end mode.
In the prior-art tape cassette, the upper cassette half 2 and the lower cassette half 3 are both made of a black (light absorption property) resin so that the light emitted from the light emitting element 27 of the tape cassette which is inserted into the video tape recorder is hardly reflected irregularly within the housing of the tape cassette. Also, light from various light sources located outside the tape cassette cannot pass through the upper cassette half 2 into the inside of the tape cassette to be reflected on its inside wall and leaked to the outside through the light receiving windows 21, 26. Consequently, the start sensor 28 and the end sensor 29 are prevented from malfunctioning.
With the spreading use of video tape recorders, however, it is desirable that a tape cassette for a video tape recorder be formed as a so-called color tape cassette. We have made experiments wherein colors of the upper cassette half 2 and the lower cassette half 3 are changed to colors other than black, for example, gray and green. Experimental results revealed that as shown in FIG. 4, an irregularly-reflected light L.sub.3 from the bottom plate 3d of the lower cassette half 3, an irregularly-reflected light L.sub.4 from the reel flange 8B, an external illumination light L.sub.5 passing through the upper cassette half 2 and so on enter the end sensor 29 through the light receiving window 26. There is then presented a problem that the end sensor 29 is caused to malfunction when the magnetic tape 4 is not in the end mode. The start sensor 28 suffers from a similar problem.
Japanese Laid-open Utility Model No. 62-98086 discloses a tape cassette in which while the color thereof remains black, a light-shielding wall is provided near the light receiving window 26 so as to close the spacing between the guide pole 11 and the side wall 3c of the lower cassette half 3, in order to improve the operation of the end sensor 29. The above-mentioned light-shielding wall, however, cannot be formed without difficulty because the guide pole 11 is generally made of metal. In addition, the light-shielding wall is effective only for an incident light irregularly-reflected from the direction of the guide pole 11.